Typical inserts used for ski boots are designed to make the foot more comfortable while skiing. Such inserts are made of foam or cork and thus deform and cushion the foot. However, these inserts have a disadvantage, in that they do not efficiently transfer the movement of the foot to the boots and, hence, to the edges of the skis. As ski design technology becomes more advanced and skiers are capable of travelling at greater speeds, the ability to efficiently control the weighting of the ski's edges becomes more critical.
There is an additional difficulty caused by the fact that an individual's feet are rarely "perfect". Most people have some degree of pronation of supination to their feet. This misalignment is aggravated by the stresses imposed on a skier's body during skiing. While some people may compensate for foot misalignment by exaggerating other movements, this method of skiing is, at the very least, inefficient and, in the worst case, can cause serious bodily injury. For example, some people with pronated feet use excessive knee action or "travel" to weight the edges of their skis. This is both tiring to the skier and potentially harmful to the skier's knees.
Typical running shoe orthotics, while they may compensate for misalignment of the foot, are not useful for skiing. Running shoe orthotics are designed for an "active" foot, one that is constantly moving within the running shoe. Hence, a large degree of cushioning is required. Even running shoe orthotics with a hard base plate require overall cushioning. In contrast, ski boot orthotics must be designed for a more "static" foot. It is undesirable to have the foot move within the ski boot. Instead, substantially all of the movement of the foot should be transferred to the boot as efficiently as possible and, hence, to the ski and the ski edges.